The present invention relates to finishing surfaces for metal molded products, such as for a vehicle wheel.
Metal products having well finished surfaces with a bright shine or lustre require the use of expensive metals. In addition, surface finishing is usually done by hand, i.e., manually.
Today's industrial mass production techniques are, however, premised on the use of various working machines, and when a decision is made as to how to finish the surfaces of metal products, it is therefore important to determine whether the method can be used as a mass-production technique.
With respect to surface finishing of metal products, a mechanical mass-production technique for making plate materials or the like having flat and extremely well finished surfaces has been established and carried out widely.
With respect to the surfaces of molded products such as cast products, forged products, or the like, however, uneven portions exist on the surfaces so that it is difficult to mechanically finish the surfaces, particularly the concave portions. Accordingly, finishing is typically performed by hand rather than mechanically.
Since vehicle wheels are part of the overall appearance of a vehicle, the appearance of design surfaces of the wheels is regarded as extremely important from a commercial point of view.
In one conventional method, a design surface of a vehicle wheel formed through molding, such as by casting or forging, is given a bright finish in order to improve the wheel's appearance.
Since vehicle wheels can be damaged by stones or other debris, a transparent coating is formed on the brightly finished design surface so that the design surface can be protected.
However, transparent coatings are not perfectly transparent, and the brightness of the design surface is therefore diminished.
Conventionally, the finishing of such a design surface is sufficiently bright so as to be recognized by human eyes through the transparent coating formed on the surface.
Recently, the transparency of transparent coatings has been improved with advances in techniques for applying such transparent coatings. However, minute defects on the design surface caused by the finishing process, or by the unevenness of the finishing, can be recognized as a result of the improvements in the transparency of the transparent coatings. That is, the improved transparent coatings allow defects to be seen and may adversely affect the appearance of the wheels.